Sculptor Dwarf Galaxy
Dwarf spheroidal Galaxy in the constellation Sculptor
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Metallicity
The metallicity of Sculptor dwarf appears to be broken up into two distinct groups, one with [Fe/H] = −2.3 and the other with [Fe/H] = −1.5. Similar to many of the other Local Group galaxies, the older metal-poor segment appears more extended than the younger metal-rich segment. Using cosmological numerical simulations, it has been recently argued that Sculptor's two distinct stellar populations would be the tell-tale sign of a past merger between Sculptor and another small dwarf galaxy companion.
The Sculptor Dwarf is home to the most metal-poor star outside of the Milky Way, known as AS0039, with a metallicity of [Fe/H] = −4.11. Unlike other known metal-poor stars, it has a low carbon abundance and an unusual ratio of alpha elements, suggesting it may have been formed in the aftermath of a Population III star hypernova.
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Measurements
Using both Hubble Space Telescope and Gaia observations 12 years apart, about 100 stars in the galaxy were mapped accurately, and 3D motions of about 10 of those stars enable trajectories to be mapped as well.